1. Field of the Invention
The present invention relates to an operating method of an access point (AP) and a station, and more particularly, to an operating method of an AP and a station for a coexistence of basic service sets having different bandwidths.
2. Description of the Related Art
When networks having different channel bandwidths are mixed in a wireless local area network (WLAN) environment, a station (STA) in a short range network may lose a channel access opportunity due to an STA in a relatively long range network since signals having different bandwidths have different ranges. In particular, a long range STA not sensing transmission performed by a pair of short range STAs may initiate transmission while the pair of short range STAs are performing transmission. In this example, when any one of the short range STAs is positioned within a range of the long range STA, a collision may occur with respect to transmission of the corresponding short range STA. In order to alleviate such a collision, before the pair of short range STAs initiate data transmission, a long range Request to Send (RTS) signal and a Clear to Send (CTS) signal may be exchanged to protect subsequent short range data transmission. However, according to the aforementioned method, the long range RTS signal and the CTS signal may have a greater overhead than a short range RTS signal and a CTS signal. Thus, when the long range RTS signal and the CTS signal are added at every data transmission, a serious overhead may occur.
When a short range basic service set (BSS) supports not only an STA using a single bandwidth but also an STA using various bandwidths, a bandwidth duplicate mode in which all such STAs may receive data may be required. The bandwidth duplicate mode includes, for example, a non-high throughput (HT) duplicate mode of the Institute of Electrical and Electronics Engineers (IEEE) 802.11ac standard. The non-HT duplicate mode may use an RTS signal and a CTS signal of a 20 megahertz (MHz) non-HT format, and send an RTS signal and a CTS signal of an identical non-HT format at every 20 MHz when a channel bandwidth of the BSS is greater than or equal to 20 MHz, for example, 40, 80, or 160 MHz. According to the aforementioned method, in a band, for example, sub 1 gigahertz (GHz) of the IEEE 802.11ah standard, in which a regulation on a maximum power transmissible per bandwidth of an apparatus performing wireless communication is present, an amount of power transmitted per unit bandwidth, for example, 20 MHz for a case of the IEEE 802.11ac standard, may decrease as an in-use bandwidth increases. Thus, a range of each RTS signal may also decrease.